Pallets are a common device used for stowing and transporting items during shipping. Pallets typically consist of a top deck, a bottom skid, and several supports positioned in between such that there is space between the top deck and bottom skid. The space allows for the tow forks of a fork lift truck to be positioned in between the top deck and bottom skid such that the pallet, and hence anything stowed on the pallet, is able to be lifted and moved from one place to another. This is especially useful when items are being loaded and unloaded during shipping.
In the past, pallets were generally made of wood, but there has been an increasing interest in making pallets out of plastic materials because pallets made of plastic are more durable than pallets made from wood. However, pallets must possess certain strength requirements. More specifically, the supports must be able to withstand the impact from the forks of the fork lift or other vehicle used for moving the pallets, as well as support the load placed on the pallet. Pallets are commonly exposed to impact from the tow forks from a fork lift because they are moved so frequently, and used for transporting various items on essentially a daily basis.
Attempts to make pallets out of plastic composite materials have proven to be unsuccessful. One of the reasons for this is that in order for the posts to posses the proper amount of strength to resist impact from tow forks, the posts must have a certain thickness; they must be manufactured with a thickness of nine millimeters to possess the proper strength. However, for typical injection molding cycle times, wall stock thicknesses of the posts should be between three and six millimeters. Posts with the typical wall thickness of three to six millimeters (which are common injection molding wall thicknesses), cannot absorb impact from tow forks; the fork penetrates the post upon impact. Conversely, plastic material having a thickness of nine millimeters (which provides sufficient resistance to tow fork impact) requires longer molding cycle times, which is considered undesirable and uneconomical.
Another approach to solving this problem is to use high-density polyethylene (HDPE), which has the ability to stretch under load applied from tow forks, with an integrated steel roll reinforcement, such as steel roll formed sections or pipes to carry loads which are contained within a welded HDPE assembly. Using this design is often considered undesirable because it is so costly.
Accordingly, there exists a need for an improved manufacturing method for making pallets out of a composite material.